Not applicable.
Not applicable.
The invention is related to bundle pullers and, more particularly, to a bundle puller having an adjustable length carriage frame.
Shell and tube heat exchangers constitute a substantial portion of the heat transfer equipment in oil refineries and other chemical processing plants. The transfer of heat between two streams at different temperatures is accomplished by flowing one stream through tubes that are arranged in a bundle, and flowing the second stream past the outside of the tubes on the shell side.
Scale and sediment build up on both the outside and inside of the tubes during use. Over time, these deposits decrease the efficiency of the heat transfer across the tube walls. Cleaning the heat exchanger usually involves hydro-blasting the inside and outside of the tubes, as well as the inside of the shell. Examples of the cleaning process may be found in U.S. Pat. No. 4,323,398 and U.S. Pat. No. 3,938,535, which are incorporated herein by reference. Before cleaning, the tube bundles have to be extracted or pulled from the shell. Pulling the tube bundle of a heat exchanger requires a significant amount of force to break the bundle loose from where it has adhered to the shell.
A number of techniques are available for pulling the tube bundle from the shell. For example, U.S. Pat. No. 4,575,305, which is hereby incorporated by reference, discloses a truck mounted bundle puller. The truck mounted bundle puller includes a vertical telescoping column rotatably mounted to the rear of a truck bed, and a carriage frame mounted to the top of the telescoping column. The carriage frame has a sled mounted thereon to engage an end of the tube bundle, and is adapted to slide along the carriage frame. A hydraulic screw drive carried by the carriage frame is used to move the sled along the carriage frame to thereby pull the tube bundle from the shell.
The carriage frame for a typical truck mounted bundle puller has a fixed length of about 24 feet to allow pulling tube bundles of up to 20 feet in length. One of the reasons for the fixed length is because of the use of the screw drive to move the sled. FIG. 1 shows an example of an existing carriage frame 10 having a fixed length. As can be seen, the carriage frame 10 includes two carriage frame arms 12 and 14. A sled 16 rests on top of the two carriage frame arms 12 and 14 and can be slid back and forth to remove and install a tube bundle 18. The sled 16 is engaged with, and driven by, a threaded shaft or drive screw 20 disposed between the two carriage frame arms 12 and 14.
The drive screw 20 is rotatably attached at one end to the end of the carriage frame 10 that is closest to the tube bundle 18. The other end of the drive screw 20 is fixedly attached to a drive motor or similar means (not shown) for rotating the drive screw 20. In operation, the drive motor or similar drive means rotates the drive screw 20 to thereby move the sled 16 back and forth along the length of the carriage frame arms 12 and 14. In order for this arrangement to be effective, however, the drive screw 20 must be anchored to the ends of the carriage frame 10. As a result, the length of the drive screw 20 and, hence, the length of the carriage frame 10, is necessarily fixed.
This fixed length causes problems for many older refineries that have narrow alleyways because the carriage frame cannot easily fit through the narrow alleyways or make the turns necessary to line up on the axis of the heat exchanger in order to pull the bundles. Thus, a large number of truck mounted bundle pullers are precluded from operation in these older refineries, requiring resort to more expensive, less efficient methods for pulling the bundles. Specialized truck mounted bundle pullers with shorter fixed length carriage frames have been created specifically for use in refineries with narrow alleyways, but this also is more expensive and less efficient. In addition, the shorter carriage frames are difficult, perhaps even unsafe, to use with longer tube bundles because of the uneven balancing resulting from a longer tube bundle on a shorter carriage frame.
Accordingly, there is a need for a bundle pulling apparatus that will efficiently and safely handle tube bundles of different lengths and that will be easily manageable within congested refineries and chemical plants. In order to do this, it is necessary to provide a carriage frame that does not have a fixed length, even though this may hamper the use of proven sled-moving apparatuses. More specifically, it is necessary to provide a carriage frame that can be shortened or lengthened as needed to accommodate different size alleyways and tube bundles.
The present invention is related to a bundle puller having an adjustable length carriage frame. The carriage frame includes a hinged section that can be rotated between a level or lowered position and a raised position. When the hinged section is raised, the length of the carriage frame is decreased considerably, which allows the bundle puller to be operated in narrow alleyways. The hinged section may then be lowered for operating in larger alleyways and when operating to remove tube bundles for cleaning. One or more hydraulic cylinders lower and raise the hinged section. A rack-and-pinion drive system is used instead of the more common screw drive system to move the sled back and forth on the carriage frame while removing or replacing tube bundles in the heat exchanger shell. Separate gear racks are attached to the hinged section and main section of the carriage frame, respectively. The separate gear racks can be raised and lowered with the hinged section. These separate gear racks are oriented to be aligned with each other when the rack is in its operational mode.